The present invention relates in general to centrifuge designs for separating particulate matter out of a circulating fluid. Suitable particulate separation mechanisms for the present invention include spiral vane and cone-stack technologies, to name two of the possibilities. More specifically, the present invention relates to the use of an impulse turbine as a part of the overall drive mechanism that is used to impart rotary motion to the rotor assembly of the centrifuge. While a cone-stack or spiral vane particulate separation mechanism will preferably be positioned within the rotor shell as the preferred particulate separation means, the present invention is not limited by the type of particulate separation means which may be selected. The cone-stack and spiral vane styles of particulate separation means are believed to represent two of the more efficient arrangements and are selected for the preferred embodiment, in part, for this reason.
It is also helpful to understand the structure and functioning of one of the earlier centrifuge designs which uses an impulse turbine in cooperation with a particulate separation mechanism as part of the rotor design. One such earlier centrifuge design is disclosed in U.S. Pat. No. 6,017,300 which issued Jan. 25, 2000 to Herman. This '300 patent is expressly incorporated by reference herein for its disclosure and teaching of the overall centrifuge design and the use of a cone-stack subassembly as part of that centrifuge design. More specifically, the '300 patent discloses a cone-stack centrifuge which is designed for separating particulate matter out of a circulating liquid, using a cone-stack assembly. This cone-stack assembly is configured with a hollow rotor hub and is constructed to rotate about an axis. The cone-stack assembly is mounted onto a shaft centertube which is attached to a hollow base hub of a base assembly. The base assembly further includes a liquid inlet, a first passageway, and a second passageway which is connected to the first passageway. The liquid inlet is connected to the hollow base hub by the first passageway. A bearing arrangement is positioned between the rotor hub and the shaft centertube for rotary motion of the cone-stack assembly. An impulse-turbine wheel is attached to the rotor hub and a flow jet nozzle is positioned so as to be directed at the turbine wheel. The flow jet nozzle is coupled to the second passageway for directing a flow jet of liquid at the turbine wheel in order to impart rotary motion to the cone-stack assembly. The liquid for the flow jet nozzle enters the cone-stack centrifuge by way of the liquid inlet. The same liquid inlet also provides the liquid which is circulated through the cone-stack assembly for the separation of particulate matter.
The impulse-turbine wheel of the '300 patent is attached directly to the rotor hub and a driving fluid is used to impinge onto the open side of the buckets of the is impulse-turbine wheel. This driving fluid may either be a portion of the incoming fluid to be processed, typically oil, see FIGS. 1 and 1A of the '300 patent, or an auxiliary fluid, such as air, water, etc., see FIGS. 6 and 6A of the '300 patent. The bucket style may take on a variety of configurations, including the modified half bucket style and the conventional Pelton (split bucket) style, both of which are specifically disclosed in the '300 patent.
Having considered the design, construction, and operation of the apparatus of the '300 patent, it was recognized that improvements would be possible as part of the design of a fully disposable, molded plastic centrifuge rotor. One of the features of the present invention is the use of a gear drive to impart rotary motion to the rotor (assembly) of the centrifuge. One of the reasons for using gears to drive the centrifuge rotor is to be able to use different input mechanisms and increase or decrease the gear reduction or gearing ratio, thereby leading to slower or faster rates of rotation (RPMs) for the rotor (i.e., slower or faster centrifuges). Using gears not only increases the flexibility of the centrifuge design, but also allows for greater design freedom for selected other components, such as the bearings. When the centrifuge gear drive is combined with an impulse turbine, as disclosed by the present invention, the design freedom extends to the impulse turbine as well. The bearings and impulse turbine are both critical to the life and speed of the centrifuge package. Since the bearings are not disposable and are expensive, they need to last until the engine is overhauled. On smaller centrifugal units without gears, the outside diameter of the bearing drives the design of the impulse turbine which in turn limits performance and speed. The solution is to optimize the gear drive-impulse turbine relationship and the design of these individual component parts as part of the molded gear drive of the present invention.
The optimization of the present invention relates to the range of volumetric flow (gallons per minute (GPM)) that goes through the nozzle and is directed at the impulse turbine. With the volumetric flow rate set or selected, the next decision is to size the driven gear (arranged as part of the lower or bottom component of the rotor housing) for a given speed based on the customer's requirements. The gear ratio between the driving gear and the driven gear can be modified to include a broad range of speeds and applications.
Having a gear drive allows for another design challenge to be addressed. The direction of the nozzle is critical to the speed of the centrifuge. Using the gear drive allows for the nozzle and impulse (Pelton) turbine to be placed on an alignment carrier which takes care of any manufacturing alignment issues. This particular design of the present invention enables preselection of an optimum gear ratio for proper turbine performance at the target rotor speed. Having the impulse (Pelton) turbine separate from the rotor assembly prevents the disposal of the expensive impulse (Pelton) turbine at the time of the disposal of the rotor assembly.